Engine cylinders are typically formed by attaching cylinder heads to cylinder blocks. In engine design there are trade-offs between strength, weight, and other material properties of materials used to construct the cylinder head and block. For example, iron has been used to manufacture cylinder blocks. Cast iron may have several benefits over other materials such as a smaller volume to strength ratio and a smaller friction coefficient, decreasing the engine's size and combustion chamber wear. However, cast iron cylinder blocks may have a low strength to weight ratio, is more susceptible to corrosion, and has undesirable heat transfer characteristics. To reduce weight and increase heat transfer to water jackets, cylinder block may be cast out of aluminum. However, aluminum cylinder blocks have several drawbacks, such as high friction coefficients and larger volume to strength ratios.
U.S. Pat. No. 5,370,087 discloses an engine having a composite cylinder case enclosing metal cylinder banks. The inventors have recognized several disadvantages with the cylinder block disclosed in U.S. Pat. No. 5,370,087. Firstly, the cylinder case enclosing the cylinder banks is spaced away from the cylinder banks to enable coolant to flow around the cylinders. This type of arrangement decreases the structural integrity of the engine when compared to engines cast via a single continuous piece of metal. Therefore, forces transferred to the engine via external components, such as the transmission, may damage the cylinder case. As a result, the longevity of the engine is decreased.
The inventors herein have recognized the above issues and developed an engine. The engine includes a thermo-molded composite cylinder block including a front engine cover attachment interface and a transmission attachment interface. The engine further includes a cylinder liner comprising a different material than a composite cylinder block and integrally molded with the composite cylinder block, the cylinder liner defining a portion of a boundary of a cylinder and including a top deck at least partially extending across a water jacket cavity surrounding the cylinder.
In this way, a composite material integrally molded with a cylinder liner may be used to form a portion of the engine to increase the engine's strength to weight ratio. Furthermore, the cylinder liner may comprise a metal or other suitable material having more desirable abrasion and heat transfer characteristics around the combustion chambers. In this way, selected portions of the cylinder block may be designed with different materials to increase the engine's strength to weight ratio without compromising desired combustion chamber characteristics. Moreover, integrally molding the cylinder liner with the cylinder block increases the coupling strength of the block assembly.
The cylinder liner may include various structural features providing greater coupling strength between the cylinder liner and cylinder block. For example, the liner may include a block attachment recess in a top deck of the cylinder liner as well as a block attachment lip extending around a peripheral surface of the liner. The contours of these features provide a greater amount of bonding strength between the thermo-molded composite cylinder block and the cylinder liner during molding. Additionally, the top deck may include openings in fluidic communication with a water jacket cavity. The openings enable a filler material, such as wax, to flow out of the mold during manufacturing. In this way, the water jacket cavity may be formed during manufacturing. Additionally, the openings in the top deck also enable vapor to escape the cylinder block water jacket during engine operation.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. Additionally, the above issues have been recognized by the inventors herein, and are not admitted to be known.